The invention is concerned with a microemulsion of the oil-in-water type, containing at least one polyglycerol ester as the emulsifier and at least one lipophilic substance as the internal phase.
Certain substances, which can be used for the manufacture of a microemulsion, lead to microemulsions which can be used without hesitation in foodstuffs or in the pharmaceutical or cosmetic field for human beings. For example, in the pharmaceutical field microemulsions have been manufactured using tensides as emulsifiers, which contain polyoxyethylene residues in the hydrophilic part of the chain. With the aid of these tensides even fat-soluble substances, such as e.g. vitamins or pharmaceutically active substances, can be solubilized in water to give a clear emulsion. However, these emulsifiers can be harmful to health. Use in foodstuffs is accordingly prohibited, mainly because these tensides contain residual monomers which are potentially carcinogenic.
Great Britain Patent Publication GB 2,222,770 describes microemulsions having sugar esters as emulsifiers, which contain as essential co-emulsifiers low-molecular polyoxyethylenes which are, however, toxic.
U.S. Pat. No. 5,045,337 describes for the foodstuff field, a water-in-oil microemulsion system with polyglycerol esters or mono-diglycerides as emulsifiers for the formulation of hydrophilic vitamins and flavorants.
U.S. Pat. No. 4,835,002 describes oil-in-water microemulsions with polyglycerol esters for the formulation of lipophilic edible oils, fragrance-imparting oils or flavor-imparting oils, which are proposed for the foodstuff field.
The present invention is concerned with an oil in water microemulsion which comprises as an emulsifier, at least one polyglycol ester, the polyglycol ester being a triglycerol monofatty acid ester; at least one lipophilic substance selected from the group consisting of carotenoids, vitamin A and its derivatives, vitamin D and its derivatives, vitamin E and its derivatives, vitamin K and its derivatives, and polyunsaturated fatty acids, and combinations thereof; and water.
The microemulsion is characterized in that the emulsifier contains at least one triglycerol monofatty acid ester and the lipophilic substance is selected from the group of carotenoids, especially xcex2-carotene, vitamins A, D, E and K and their derivatives and polyunsaturated fatty acids such as e.g. arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid.
Derivatives of the vitamins are, for example, vitamin A acetate, vitamin A palmitate, vitamin E acetate and the like. Under vitamin E there is to be understood synthetic of naturals tocopherols.
With this microemulsion it is possible to solubilize the afore-mentioned lipophilic substances in any amount of water without changing the microscopic appearance of the microemulsion or without breaking the microemulsion.
The emulsifiers used are non-toxic and, accordingly, such microemulsions can be used in foodstuffs. They can also be used in the pharmaceutical field. Cosmetic formulations are likewise possible.
Preferred triglycerol monofatty acid esters are triglycerol monolaurate, triglycerol monocaproate or triglycerol monocaprylate, especially triglycerol monolaurate or triglycerol monocaprylate.
The microemulsions can be manufactured with or without a co-emulsifier. Preferred co-emulsifiers are ethanol, propylene glycol, transcutol (diethylene gylcol monoethyl ether, available from Gattefosse S.A., France), polyethylene glycols, polyglycerols, monoglycerides or lecithin, especially transcutol, monoglycerides or lecithin, with lecithin being especially preferred.
Furthermore, the microemulsion can also contain at least one carrier oil. The lipophilic substance is dissolved at least in part in the carrier oil, which increases the final content of lipophilic substance in the finished microemulsion. The carrier oil is preferably orange oil, palm oil, a triglyceride, squalane, squalene, limonene, isopropyl myristate or isopropyl palmitate, especially orange oil, squalane or limonene, preferably orange oil.
The microemulsion contains as the vitamin especially tocopherol and/or vitamin A, especially vitamin A palmitate.
As the carotenoid the microemulsion preferable contains all-trans-xcex2-carotene, 9-cis-xcex2-carotene, 13-cis-xcex2-carotene, xcex2-opo-8xe2x80x2-carotenic acid ethyl ester, apocarotenal, astaxanthin, canthaxanthin, crocetin or lycopene. A xcex2-carotene is especially preferred.
Preferably, the amount of lipophilic substance, for example tocopherol, lies at 1-20 wt. %, the amount of emulsifier lies at 10-99 wt. % and the amount of co-emulsifier (when present) lies at 1-89 wt. %, with the ratio of emulsifier to co-emulsifier preferably being 50:50 wt. %.
The microemulsion can be used especially in foodstuffs, in pharmaceutical preparations and in cosmetics.
For foodstuffs, the oil in water microemulsions of the present invention provide a convenient way to add or fortify a variety of foodstuffs, for examples, beverages, baked goods, dressing, and the like, with the lipophilic substances mentioned herein. The same holds true for pharmaceutical compositions and cosmetics. For pharmaceutical compositions, the oil in water microemulsions permit the addition of the lipophilic substance to pharmaceutical compositions, for example, oral vitamin solutions. For cosmetics, the oil in water microemulsions permits the addition of the lipophilic substances to variety of cosmetics, for example, foundation, lipstick, and the like.
In each instance for foodstuff, pharmaceutical, and cosmetic materials, the addition of the lipophilic substances mentioned herein provide valuable properties to the materials as one of ordinary skill in the art will appreciate when such lipophilic substances are either consumed (foodstuffs or pharmaceuticals) or are topically applied (pharmaceuticals or cosmetics). For the various foodstuff, pharmaceutical and cosmetic materials, the amounts of oil in water microemulsion to be added will depend upon the amount of lipophilic substance that is desired to be added to the material and the effect which the lipophilic substance is to have, for example, antioxidant effect or intaking the recommended daily allowance of the lipophilic substances.
In the case of foodstuffs, by fortifying the foodstuffs with the oil in water microemulsion of the present application, the lipophilic substance incorporated by use of the microemulsion provides for levels of the lipophilic substance which would be greater than that present in the foodstuff without the addition of the microemulsion. In the case of cosmetics, by adding the microemulsion of the present invention, the cosmetics can be fortified with many of the lipophilic substances which are considered useful in treating wrinkles, burns, etc. In the case of pharmaceuticals, using the microemulsions of the present invention permits valuable formulations to be fortified with, for example, the lipophilic substances mentioned herein to make vitamin solutions and other medicaments to be prepared.
The microemulsion in accordance with the invention is especially suitable for formulations in which the aforementioned lipophilic substances need to be solubilized as lipophilic pharmaceutically active substances. Thus, tocopherol is especially useful as the lipid.
The microemulsion is dilutable or miscible with water in any ratio. A pharmaceutically convenient dilution of the microemulsion contains e.g. 90 wt. % water. In this formulation 0.1-2 wt. % tocopherol would then be present.
The speed of the microemulsion formation depends on the velocity at which the individual components dissolve. When e.g. salve-like emulsifiers, such as, for example, triglycerol monolaurate, are used, the speed at which these emulsifiers dissolve can be accelerated by slight stirring and possibly warming to about 40-45xc2x0 C. A magnetic stirrer is suitable for this purpose. However, a different stirrer or any heating system can be used. The formulation is finished when a clear, isotropic liquid has formed from the individual components, which usually occurs after several minutes.
The formulations can additionally contain flavorants, colorants and/or thickeners when their use requires this to be the case. If the content of polyglycerol esters amounts to less than about 3-5%, the formulation can be additionally preserved with conventional preservatives.
Further features and particulars will be evident from the following Examples.